The present invention relates to a burner for raising the temperature of exhaust gas and, in particular, to a premixing type burner in which a mixture of fuel and air is supplied to a combustion chamber.
Conventional diesel engines include, in the exhaust passage, a diesel particulate filter (DPF), which captures particulate matter (PM) contained in exhaust gas. In such a DPF, in order to maintain the function of capturing particulate matter, a regeneration process, in which particulate matter captured by the DPF is burnt using exhaust gas, is performed.
For example, Japanese Laid-Open Patent Publication 2011-185493 discloses an exhaust purification device in which combusted gas is generated by combusting a mixture of fuel and air in a combustion chamber of a burner arranged upstream of the DPF. Supply of combustion gas to exhaust gas in the exhaust passage raises the temperature of the exhaust gas that flows into the DPF.
As such a burner, a premixing type burner is known that supplies a mixture of fuel and air to the combustion chamber without separately supplying fuel and air to the combustion chamber to improve the ignitability or the combustibility of the air-fuel mixture, thereby reducing unburned fuel contained in the combustion gas.
Combustion gas generated by the aforementioned premixing type burner contains more than a little unburned fuel. Since the unburned fuel is not used to generate the power of the engine, it is preferable to reduce the fuel used for increasing the temperature of the exhaust gas to reduce the amount of fuel consumption in the vehicle including the engine. Thus, it is desired to reduce unburned fuel on combustion so that fuel required for obtaining a predetermined heat amount is reduced.